After a month of waiting, a tiny but crucial bit of progress:



I sent the crankshaft from my FS-40S-CX to a machinist who's done work for me several times in the past, and I asked him to grind-down the last 5mm of the crankshaft from an 8mm diameter to a 7mm diameter. This will allow a normal nitro flywheel collet to fit the crankshaft.